Field of the Invention
The present invention relates generally to cement mixers, and more particularly to manually operated cement mixers, and still more particularly to a manually operated cement mixer having a plurality of mixing troughs.
Background Discussion
Concrete is the most wide used manmade construction material in the world. In the United States alone, concrete production and installation is a $35 billion industry, employing more than two million workers. Approximately 7.5 billion cubic meters of concrete are made each year—more than one cubic meter for every person on Earth.
QUIKRETE, of Atlanta, Ga., is the nation's largest manufacturer of packaged concrete and cement mixes and has more than 90 manufacturing facilities in the United States, Canada, Puerto Rico and South America, so that it can meet the customer demand for its products. That demand comes from both trade professionals and amateur “do-it-yourselfers.” Each year concrete is used for hundreds of thousands of small and large projects: cementing fence posts and mailbox posts, pouring steps, concrete slabs, small foundations, and footings for walls, and so forth. The variety of tasks is nearly endless. [QUIKRETE is a registered trademark of Quikrete, International, Inc., of Atlanta, Ga..]
Traditionally, concrete for small jobs is mixed offsite and delivered in small mixer trailers, or it is mixed on-site using electric mixers ranging in size from 1.5 cubic feet to 6-9 cubic feet. The shortcoming in using such mixers is that they require electrical power and are difficult to transport and store. Further, they can range in cost from a few hundred dollars to several thousands of dollars, depending on size and quality.
For the do-it-yourself homeowner, when faced with a small concrete job requiring small volumes of concrete, there are three options typically considered for mixing the concrete manually: The first is to mix the concrete in a wheelbarrow or a bucket; the second is to use disposable concrete mixing bags, with costs hovering at about $90 for a 12-pack; and the third is to mix on a disposable tarp. In all three cases, the job requires a great deal of work over and above mixing concrete, particularly when it comes to cleanup.
As an option, and electric motor driven cement mixer can be employed. These mixers can mix from 1 to 9 cubic feet of concrete in a batch and generally cost between $300 and $2,000 depending upon the size and quality of the machine. In addition they are heavy and difficult to operate. Well-known examples include the Cleform Gilson 400UT towable mixer, the KPRO 3.6 or KPRO 6 from Kushlan Products, and the Buffalo Concrete Mixer from Cleveland Steel Tool of Cleveland, Ohio. If a power supply is not available for any of these mixers, use of such an electrically powered mixer is simply not an option. Those needing a non-electric solution often resort to the use of buckets or wheelbarrows, each of which requires considerable physical strength and effort.
An alternative to wheelbarrows, tarps, and buckets can be found in U.S. Pat. No. 1,505,263, to Hewitt. This antique patent teaches a mixer having a container pivotally mounted in a frame and provided with handles for manually oscillating the trough back and forth. The trough is configured with sides that curve gradually and uniformly inwardly so as to “prevent the formation of eddies in the load as it is agitated.” Indeed, at several points in the disclosure, the patentee in Hewitt '263 emphasizes that the “peculiar configuration of the bottom of the trough serves to prevent eddies and the like.”
The patent to Hewitt was an inspiration for the present invention, inasmuch as it initially appeared to represent a viable alternative to other manual means of mixing concrete. However, experiments with the apparatus described in the '263 patent showed it to be deficient in several respects, notably relating to the configuration of the trough bottom. After constructing a faithful replica of the apparatus taught in the '263 patent, tests conducted showed that the basic principle of an oscillating mixer generally works for its intended purpose. That is, tilting a mixing trough to the right moves the cement, sand, gravel and water to the right compartment of the trough. As the trough is brought back to its, neutral, central position, the slurry is accelerated down the side of the trough, through the curved bottom of the right compartment and sent spilling over the medial rib. Continuing past the central point and tilting the mixing trough to the left moves the remaining slurry to the left compartment of the trough. Again, as the trough is brought back to its, neutral, central position, the slurry is accelerated down the straight side of the trough, through the curved bottom and sent spilling over the medial rib.
However, the apparatus described in the '263 patent was shown to require considerable time and effort to completely and thoroughly mix (completely wet) a dry cement composition. Testing suggested that it was precisely the configuration of the '263 trough bottom that presented the problem to be overcome yet taught no solution to the problem.
It is respectfully submitted that none of the known prior art systems and apparatus, including Hewitt '263, include, disclose, teach, suggest, show, or otherwise render obvious, either singly or when considered in combination, the invention described herein. In fact, Hewitt positively teaches away from the solution provided by the present invention.